This application is based on Patent Application No. 2000-348643 filed Nov. 15, 2000 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an ink jet print head and an ink jet printing apparatus using the same ink jet print head.
2. Description of the Related Art
There are various types of ink jet printing apparatus for performing printing on a printing medium by ejecting ink from an ink ejection opening and an ink jet print head used in the ink jet printing apparatus. Among these, typical examples of ink supply method to the ink jet print head include the following.
First, as a first type, there is a type in which using a tube from an ink vessel containing the ink, ink is supplied to the ink jet print head through a filter for preventing fine dust from coming in the ink jet print head, in this type, when ink in the ink vessel is exhausted, the ink vessel is replaced, and in this case, for preventing bubbles from mixing in the ink jet print head, it is general that ink is suction recovered or pressure recovered from the ink jet print head. Such an ink jet printing apparatus is often used in a large-sized ink jet printing apparatus.
Further, as a second other type, there is an ink jet printing apparatus using an on-carriage type ink jet cartridge of a structure integrally including an ink vessel and an ink jet print head. Such a type is often used in a relatively small-sized ink jet printing apparatus, which is widely used because replacement or the like of the ink jet print cartridge is simple. However, in such type of ink jet cartridge, when the ink vessel is replaced at the time the ink in the ink vessel is exhausted, because ink jet print head is wasted at the same time, recently, in view of running cost and environmental problems, various kinds of on-carriage type ink jet print cartridges are often proposed which allow replacement of only the ink vessel when the ink is exhausted.
The ink cartridge used in the second type ink jet printing apparatus is generally divided into an energy generation substrate for ejecting the ink, an ink jet print chip provided with an ink ejection opening corresponding to an energy generation element incorporated in the substrate, an ink jet print head portion provided with a filter for supplying ink not containing fine dust to the ink jet print chip, and an ink vessel portion for storing the ink, when the ink vessel is replaced, it is general that a suction recovery is performed for preventing air bubbles from coming into the ink jet print head which disturb stable printing.
However, even though the suction recovery is necessary when the ink vessel is replaced, if the suction recovery is performed many times, ink consumption other than for printing is increased which greatly increases the running cost. Further, for example, as one of general-purpose ones used as energy generation means for ejecting ink of the ink print head, an electrothermal converter (heater) is used. This is one which by energizing the heater, film boiling is generated in the ink so that the ink is ejected by the force. In this ink ejection process, dissolved air contained in the ink is generated as a gas even in small amount. If such a bubble builds up to a large amount, since it has an adverse effect on printing, before the bubble present in the ink jet print head becomes a size to have an adverse effect on printing, it is necessary to perform suction recovery of the ink jet print head. Also in this case, since ink consumption not used for printing occurs, there is a problem of an increased running cost.
In an ordinary ink jet print head, for example, as shown in FIG. 6, an ink jet print head 100 has a casing 102 integral with an ink vessel like an ink tank, this casing 102 forms an ink liquid chamber 103, and a filter 104 is provided between the ink vessel. Further, in the casing 102, at the opposite side to this filter 104, an ink jet print chip portion 105 for ejecting ink to make printing is provided. The filter 104 is to remove impurities such as dust contained in the ink supplied from the ink vessel so that a clean ink is supplied into the ink liquid chamber 103. Further, in the ink liquid chamber 103, a sheet of plate member 106 is inclinedly provided, and a gap S is formed between the lower side end of the plate member 106 and the casing 102. Therefore, as shown in the figure, the ink supplied into the ink liquid chamber 103 passes through the gap S between the end of the plate member 106 and the casing 102 to be supplied to the energy generation means for ejecting the ink and the ink jet print chip portion 105 provided with an ink ejection opening for ejecting the ink, so that the ink is ejected to a printing medium to perform printing.
Further, in such an ink jet print head 100, a bubble collecting portion 108 is formed at the upper side end of the inclined plate member 106, a ventilation hole 109 is provided in the casing 102 in the vicinity of the bubble collecting portion 108, and the ventilation hole 109 is in general provided thereon with a hydrophobic film 110 of a porous material which has a property that air is passed but the ink is not passed so that the ink liquid chamber 103 and outer air are communicated through the hydrophobic film 110 with each other. However, if the ink liquid chamber 103 and outer air are only in a communication state, since ink in the ink liquid chamber evaporates, a bubble discharge portion 111 is provided which is constructed in a closed state that it is normally closed other than when bubbles accumulated in the bubble collecting portion 108. Further, as the hydrophobic film 110, a porous material such as xe2x80x9cGOATEXxe2x80x9d (tradename) or the like is used.
As shown in the figure, the bubble discharge portion 111 is formed of an enclosure 112 having an opening 113, a lid for closing the opening 113 of the enclosure 112, and a spring 115 for pressing the lid 114. It is constructed so that bubble accumulated in such a bubble collecting portion 108 flows through the hydrophobic film 110 to the bubble discharge portion 111 to be accumulated in the bubble discharge portion 111, bubble accumulated in the bubble discharge portion 111, that is, air, is discharged to the outside.
As described above, in the prior art ink jet print head 100 constructed as shown in FIG. 6, the ink is supplied through the gap S towards the ink jet print chip portion 105, and ejected from the ink jet print chip portion 105 to the printing medium to perform printing. In the ink jet print chip portion 105 in this case, a bubble B is generated by ink ejection, part of the generated bubble B moves through the gap S towards the filter 104 to be adhered to the filter 104. Moreover, such a bubble B adhered to the filter 104 will never pass through the filter 104 due to a meniscus force of the filter 104.
Therefore, in such a state, when bubble B further adheres to the filter 104, bubble B accumulates at the lower side of the filter 104, finally a malfunction occurs in ink supply from the ink vessel to the ink jet print chip portion 105, making stable printing impossible.
It is therefore an object of the present invention, in order to solve such problems in the prior art, to provide a reliable ink jet print head and an ink jet printing apparatus using the ink jet print head which is possible to remove bubbles accumulated in the ink jet print head without unnecessary ink consumption by suction recovery and at a low running cost.
In accordance with the present invention which attains the above object, there is provided an ink jet print head for ejecting ink to make printing, wherein an ink liquid chamber between a filter and an ink ejection opening for ejecting the ink has means for collecting bubbles, means for moving bubbles to the bubble collecting means, and means for discharging bubbles accumulated in the bubble collecting means to the outside, therefore, suction recovery of the ink jet print head is only in a special case such as an accident or the like, ink consumption amount due to suction recovery is greatly reduced, printing of very low running cost is possible, and a reliable ink jet print head and an ink jet printing apparatus are obtained.
Further, since, in the ink jet print head of the present invention, the bubble collecting means is inclined to the direction of gravity, and two plate members spaced with an interval are used, bubbles can be advantageously collected and discharged, thereby preventing the filter from clogging.
Still further, since, in the ink jet print head of the present invention, a hydrophobic film is used in the means for discharging bubbles to the outside, bubbles can be discharged simply and efficiently.
Yet further, since, in the ink jet print head of the present invention, the hydrophobic film is covered so that it is not exposed directly to outer air other than when removing bubbles, the hydrophobic film can be advantageously protected.
Since, in the ink jet print head of the present invention, in the means for collecting bubbles, the filter is provided inclinedly to the direction of gravity, bubbles can be advantageously conducted and collected using a simple means.
Further, since, in the ink jet print head of the present invention, the cover of the hydrophobic film is a flexible member, the hydrophobic film can be advantageously protected so that bubble are efficiently discharged.
Still further, since, in the ink jet print head of the present invention, the cover of flexible member of the hydrophobic film is provided with a ventilation hole and a check valve, the bubble discharge means can be formed to a simple construction, and bubbles can be discharged simply and efficiently.
Yet further, since, in the ink jet print head of the present invention, the bubble collecting means is combined with the means for moving bubbles, the head can be made to a simple construction.
Since, in the ink jet print head of the present invention, the hydrophobic film is formed of a porous material which passes through a gas but does not pass a liquid, only bubbles can be advantageously passed through and discharged.
Further, since, the ink jet print head of the present invention has an electrothermal converter for generating a thermal energy according to energizing as an energy utilized for ejecting the ink, the ink can be advantageously ejected to the printing medium to perform good and stable printing.
Still further, since, in the ink jet print head of the present invention, utilizing film boiling generated in the ink by the thermal energy applied by the electrothermal converter, the ink is ejected from the ink ejection opening towards the printing medium, the ink can be advantageously ejected to perform stable printing, thereby improving and maintaining the printing quality.
Yet further, since, in the ink jet print head of the present invention, printing is performed using any one of the above ink jet print heads, suction recovery of the ink jet print head is only a special case, such as an accident, ink consumption amount by recovery operation is remarkably reduced, thereby obtaining a reliable ink jet print head and an ink jet printing apparatus of a very low running cost.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.